AC Circuit/power factor

Discussion in 'Homework Help' started by ladysman217, Mar 31, 2008.

  1. ladysman217

    Thread Starter New Member

    Mar 31, 2008
    Im new to this site so dont know exactly how it works. However i would like to post a question cause i could use some help.

    I have a ac circuit
    R=7+0j ohm and L=0+10j Vsource =50<0 degrees

    the question is: what value of capacitance should i have to bring the power factor to unity?

    would you be able to tell me at least how to do it?
    i have tried using the method on the sit but i still cant get it to work.

    the answer i got when i did the question was 149.5 micro farads
  2. mik3

    Senior Member

    Feb 4, 2008
    calculate the impedance of the inductor and then calculate the value of the capacitor which gives the same impedance.

    The resistor and the inductor are in series , i think, so put the capacitor in parallel with them.
  3. silvrstring

    Active Member

    Mar 27, 2008
    You must know the frequency--or the inductance, so you can then find the frequency--to find the needed capacitor. I don't see either of these in your question.

    Also, is R in parallel with L, or are they in series? The reactive power Q you are trying to balance will be different in series vs. parallel.
  4. ladysman217

    Thread Starter New Member

    Mar 31, 2008
    thanks for the help mik3 and silvrstring.
    i worked it out.

    oh sorry, yea the freq is 50Hz and the answer is around 214micro farads.
    tanks again...